University of Minnesota
School of Physics & Astronomy

Condensed Matter Seminar

Wednesday, August 24th 2016
Speaker: Yong Wu - U.C. Riverside
Subject: Quantum Transport in Strained Graphene, Graphene Heterostructures & Few-Layer Graphene

Recently, strain engineering of graphene’s electronic properties has attracted significant attention [1]. I will report transport studies in graphene sheets with linearly-shaped strain regions created by nm-scale wide folds. We find that these strain regions act as quantum wires and waveguides. We attribute this to strain-induced pseudomagnetic fields acting as confining barriers. I will also discuss transport studies on coupled massive and massless electron systems, realized using twisted monolayer graphene/natural bilayer graphene stacks. Due to the interlayer screening, we observe a nonlinear monolayer gate capacitance. Moreover, in a perpendicular magnetic field, we observe a distinct pattern of gate-tunable Landau level crossings that enable the mass and Fermi velocity in the layers to be determined. We find different values than those of isolated layers, indicating that the interlayer interactions renormalize the band structure parameters. Additionally, novel physics in graphene under different external conditions, for example under one-dimensional (1D) periodic potentials [2] and aligned to boron nitride (BN) substrates, will also be reported. Our recent studies on natural few-layer graphene, including quantum Hall effect, Landau level transitions and new Dirac points [3] in ABA-stacked trilayer graphene will also be introduced.

[1] Nikolai N. Klimov, Suyong Jung, Shuze Zhu, Teng Li, C. Alan Wright, Santiago D. Solares, David B. Newell, Nikolai B. Zhitenev, and Joseph A. Stroscio. Electromechanical properties of graphene drumheads. Science, 336(6088):1557–1561, 2012.

[2] Cheol-Hwan Park, Young-Woo Son, Li Yang, Marvin L. Cohen, and Steven G. Louie. Electron beam supercollimation in graphene superlattices. Nano letters, 8(9):2920–2924, 2008.

[3] Maksym Serbyn and Dmitry A. Abanin. New dirac points and multiple Landau level crossings in biased trilayer graphene. Physical Review B,
87(11):115422, 2013.

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